Does breast cancer cause an armpit lump?

An armpit lump is not a diagnosis by itself. Enlarged lymph nodes may also follow an infection, vaccination, skin inflammation, or another non-cancerous cause.

Breast lymph fluid drains toward lymph nodes in the armpit. Breast cancer cells can reach these nodes and make one or more feel enlarged, firm, or different from the opposite side.

A clinician considers the lump's location and texture alongside breast changes such as a new breast mass, nipple inversion, discharge, skin dimpling, or redness. Examination and imaging are needed to identify the cause; touch alone cannot confirm it.

Arrange a medical appointment for a new, unexplained, persistent, or growing armpit lump. Note when it appeared, whether it is tender, and whether you recently had an infection, vaccination, breast change, or arm injury.

The assessment may include examination of both breasts and armpits. Depending on the findings, the clinician may arrange ultrasound, breast imaging, or a needle sample from the lump.

Seek prompt assessment if the lump is hard, fixed, enlarging, or accompanied by a new breast lump, nipple discharge, nipple pulling inward, or breast skin dimpling. These features require evaluation but do not establish the cause.

Get urgent care for rapidly spreading redness, severe pain, high fever, marked swelling, or feeling seriously unwell, because an infection may need timely treatment.

Ask what features were found on examination, whether breast or armpit imaging is appropriate, and how you will receive the results. If sampling is recommended, ask what the procedure involves and what follow-up will be arranged.